As we come back to you, we have some breaking news right now. I want to go to abc's pierre thomas because there's a lpt about a package arriving at a senator's office with a deadly material inside. What can you tell us? Reporter: Sources are telling us tonight that a alert addressed to mississippi senator roger wicker tested positive for poison. These tests are notoriously unreliable but the letter is being tested again for a more definitive result. The package was intercept the at the mail facility and never reached the capital complex, but they're taking extra security precautions just in case. Just to be clear, do we have any information about anyone could have come in contact with it? It can be extremely lethal. Generally it needs to be ingested or inhaled to be dangerous to a person. We have no information that anyone pz been harmed so far, diane. I know homeland security is on top of it, as you are, pierre. We'll be back with you soon as you have more information to bring us tonight.

This transcript has been automatically generated and may not be 100% accurate.

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